X-ray spectra and time variability of active galactic nuclei

The X-ray spectra of broad line active galactic nuclei of all types (Seyfert I's, NELG's, Broadline radio galaxies) is well fit by a power law in the .5–100 keV band of mean energy slope α = .68±.15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability.On time scales longer than 12 hours most radio quiet AGN do not show strong, ΔI/I > .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristic timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable on long, τ 6 month, timescales.     

Results from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Observatory

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's.     

Ultrastructural and growth indices of Chlorella culture in multicomponent aquatic systems under space flight conditions.

Submicroscopic organization of Chlorella cells cultivated under space flight conditions in three-component aquatic system has been studied. Comparison of the experimental cells with that of the controls revealed certain rearrangements of cell organelles particularly, a reduction in the amount of reserve polysaccharides in chloroplasts, increase of cell vacuolization and mitochondrion volume, complication configuration of plasmalemma evaginations and invaginations, and also disturbances in the process of cytokinesis. More over an increase in the number of Chlorella cells infected by bacteria was shown in the experimental variant. No considerable differences were established in the growth characteristics of the experimental and control populations. A comparative cytological analysis revealed general regularities of organelles in Chlorella cells cultivated under space flight condition in the uni- and multicomponent systems.     

Corotating Interaction Regions in the Outer Heliosphere

We discuss the structure and evolution of CIRs and their successors in the outer heliosphere. These structures undergo significant evolution as they are convected to greater heliocentric distances. A progression of different types of structure are observed at increasing distance from the Sun. Similar structures are observed at similar heliocentric distance at different portions of the solar cycle. CIRs and their successors are associated with many important physical processes in the outer heliosphere. We discuss the relationship between these structures and recurrent phenomena such as cosmic ray variations, and review some of the associated theoretical models on the role of corotating structures and global merged interaction regions (GMIRs) in global cosmic ray modulation. We also discuss some outstanding questions related to the origin of non-dispersive quasi-periodic particle enhancements associated with CIRs and their successors in the outer heliosphere. This revised version was published online in August 2006 with corrections to the Cover Date.     

Acceleration of the High Speed Solar Wind in Coronal Holes

We outline a theory for the origin and acceleration of the fast solar wind as a consequence of network microflares releasing a spectrum of high frequency Alfvén waves which heat (by cyclotron absorption) the corona close to the Sun. The significant features of our model of the fast wind are that the acceleration is rapid with the sonic point at around two solar radii, the proton temperatures are high (~ 5 million degrees) and the minor ions are correspondingly hotter, roughly in proportion to their mass. Moreover we argue that since the energy flux needed to power the quiet corona in closed field regions is about the same as that needed to drive the fast solar wind, and also because at deeper levels (< 2 × 10⁵ K) there is no great difference in the properties of supergranules and network in closed and open field regions, the heating process (i.e., dissipation of high frequency waves) must be the same in both cases. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cometary Materials: Progress Toward Understanding the Composition in the Outer Solar Nebula

A major objective of the workshop was to learn about the chemical composition, physical structure, and thermodynamic conditions of the outer parts of the solar nebula where comets formed. Here we sum up what we have learned from years of research about the molecular constituents of comet comae primarily from in situ measurements of Comet 1P/Halley and remote sensing of Comets 1P/Halley, Hale-Bopp (C/1995 O1), and Hyakutake (C/1996 B2). These three bright comets are presumably captured Oort cloud comets. We summarize the analyses of these data to predict the composition of comet nuclei and project them further to the composition, structure, and thermodynamic conditions in the nebula. Near-future comet missions are directed toward less active short-period Jupiter-family comets. Thus, future analyses will afford a better understanding of the diversity of these two major groups of comets and their respective regions of origin in the solar or presolar nebula. We conclude with recommendations for determining critical data needed to aid in further analyses. Results of the workshop provide new guidelines and constraints for modeling the solar nebula. This revised version was published online in June 2006 with corrections to the Cover Date.     

Market mature 1998 hybrid electric vehicles

Beginning in 1990, the major automotive passenger vehicle manufacturers once again re-evaluated the potential of the battery powered electric vehicle (EV). This intensive effort to reduce the battery EV to commercial practice focused attention on the key issue of limited vehicle range, resulting from the low energy density and high mass characteristics of batteries, in comparison to the high energy density of liquid hydrocarbon (HC) fuels. Consequently, by 1995, vehicle manufacturers turned their attention to hybrid electric vehicles (HEV). This redirection of EV effort was highlighted finally in 1997, at the 57th Frankfurt Motor Show, the Audi Duo parallel type hybrid was released for the domestic market as a 1998 model vehicle. Also at the 1997 32nd Tokyo Motor Show, Toyota Hybrid System (THS) Prius was released for the domestic market as a production 1998 model vehicle. This paper presents a comparative analysis of the key features of these two 1998 model year production hybrid systems. Among the conclusions, two issues are evident: one, the major manufacturers have turned to the hybrid concept in their search for solutions to the key EV issues of limited range; and, heating/air conditioning; and two, the focus is now on introducing hybrid EV for test marketing domestically     

An Adaptive-Control Switching Buck Regulator-Implementation, Analysis, and Design

Describing-function techniques and averaging methods have been employed to characterize a multiloop switching buck regulator by three functionsl blocks: power stage, analog signal processor, and pulse modulator. The model is employed. to explore possible forms of pole-zero cancellation and the adaptive nature of the control to filter parameter changes. Analysis-based design guide lines are provided including a suggested additional RC-compensation loop to optimize regulator performances such as stability, audiosusceptibility, output impedance, and load transient response.     

Certain System Aspects of the Double-Sided Cyclo-Converter

A philosophy for the improvement of the extraction of controlled dc power from a polyphase ac supply line is presented. Extension of this philosophy for the interface of synchronous polyphase networks is briefly indicated. The needed kilovolt-ampere capacity of the supply line is reduced to nearly two thirds of the capacity needed for conventional controlled ac/dc converter systems. The new system requires only a small fraction of the physical weight of conventional converters. The improvements are derived from the interposition of a modulated high-power frequency carrier between the linked systems for the purpose of reconciliation of their conflicting characteristics. The harmonic content of the ac-phase currents is greatly reduced. The system operates with internal frequencies near 10 kHz; efficiencies in the upper nineties have been attained with this type of converter.     

A procedure for calculating the damping in multi-element space structures

A procedure is outlined for estimating the damping in a multi-element space structure by incorporating distributed material damping and discrete nonlinear joint properties into a linear analysis. Tests have been conducted in which the transient response of a truss member is measured in free fall in a vacuum in order to obtain precise material damping characteristics. The force-state mapping technique is then used to identify the localized nonlinearities in joints by mapping the force transmitted through the joint as a function of the full mechanical state of the joint. The identified nonlinear joint parameters are then linearized using an equivalent energy approach which finds the equivalent linear stiffness and linear viscous damping by equating the integrated work done and energy dissipated by the nonlinearity to those of a spring and damper undergoing sinusoidal motion. The distributed material damping and localized nonlinear effects are then incorporated to form a linearized damped finite element model. Finally, an eigenvalue perturbation analysis is developed to explore the effect of introducing damping at the joints on the overall dynamics of the truss, and to obtain design guidance on where supplemental joint damping might optimally be added.